---
title: "MUST defined | Agent Ready Checklist"
description: "MUST: RFC 2119 keyword for an absolute requirement. Related rows: AR-FIND-01, AR-READ-01, AR-READ-02, AR-ACT-10. Sourced example from github.com."
canonical: https://agentreadychecklist.com/glossary/must
site: "Agent Ready Checklist"
last_updated: 2026-11-05
section: "Glossary"
---

# MUST defined | Agent Ready Checklist

> MUST: RFC 2119 keyword for an absolute requirement. Related rows: AR-FIND-01, AR-READ-01, AR-READ-02, AR-ACT-10. Sourced example from github.com.

Source: https://agentreadychecklist.com/glossary/must
Site: Agent Ready Checklist
Last reviewed: 2026-11-05
Agent endpoints: https://agentreadychecklist.com/llms.txt (index), https://agentreadychecklist.com/openapi.json (API), https://agentreadychecklist.com/mcp (MCP server), https://agentreadychecklist.com/ask (search)
Access: https://agentreadychecklist.com/auth.md (no key). Pricing: https://agentreadychecklist.com/pricing.md (free).

# MUST

RFC 2119 keyword for an absolute requirement. In AgentReady v2.0 four requirements are MUST: the two changes that broke an agent, honest status codes, and an act interface. Example: AR-FIND-01, AR-READ-01, AR-READ-02, AR-ACT-10. Related rows: AR-FIND-01, AR-READ-01, AR-READ-02, AR-ACT-10. AR-READ-01 asks: Put the answer in the initial HTML: server-rendered or prerendered, not injected by a single-page app after load.

## Definition

RFC 2119 keyword for an absolute requirement. In AgentReady v2.0 four requirements are MUST: the two changes that broke an agent, honest status codes, and an act interface.

## Example

```text
AR-FIND-01, AR-READ-01, AR-READ-02, AR-ACT-10
```

## Where it appears on the checklist

-   [AR-FIND-01](https://agentreadychecklist.com/checklist/ar-find-01/)Do not block agents: Do not block agent and crawler access to public content, in robots.txt or at the network layer (WAF, bot manager).
-   [AR-READ-01](https://agentreadychecklist.com/checklist/ar-read-01/)Answer in the initial HTML: Put the answer in the initial HTML: server-rendered or prerendered, not injected by a single-page app after load.
-   [AR-READ-02](https://agentreadychecklist.com/checklist/ar-read-02/)Real HTTP status codes: Return accurate HTTP status codes: 404 or a real redirect for missing paths, 429 with Retry-After when throttling; never 200 for a missing page and never a silent challenge page in place of 429.
-   [AR-ACT-10](https://agentreadychecklist.com/checklist/ar-act-10/)An MCP server or a CLI: A product agents are expected to act on exposes at least one interface an agent can act through: an MCP server (AR-ACT-03) or a CLI (AR-ACT-06).
-   [Guide](https://agentreadychecklist.com/guides/one-day-agent-readiness-sprint/)The one-day agent-readiness sprint
-   [Guide](https://agentreadychecklist.com/guides/test-with-a-plain-fetch-client/)How to test with a plain-fetch client
-   [Guide](https://agentreadychecklist.com/guides/read-server-logs-for-agent-user-agents/)How to read your server logs for agent user agents

## Asked about it

### What is the minimum a site needs to pass AgentReady?

Meet every MUST that applies. For an informational site that is three: do not block agents (AR-FIND-01), put the answer in the initial HTML (AR-READ-01) and return real status codes (AR-READ-02). A product agents act on adds AR-ACT-10, an MCP server or a CLI.

### How many requirements are in the current AgentReady spec?

Version 2.0 (October 2026) has 24 live identifiers: 4 MUST, 14 SHOULD and 6 MAY, split across AR-FIND (4), AR-READ (10) and AR-ACT (10). AR-READ-10 is retired and its number is not reused.

## Sources

-   [github.com/agentready-org/standard/blob/main/spec/spec.md](https://github.com/agentready-org/standard/blob/main/spec/spec.md)read 2026-11-04

Last reviewed 2026-11-05. AgentReady v2.0, read 2026-11-04.